Thousands of people besieged a government office in a southern Chinese town yesterday and blocked a highway to demand a halt to a planned coal-fired power plant because of concerns about pollution, protesters said.

Riot police used tear gas in an attempt to disperse the protesters at the highway in the town of Haimen in Guangdong province, and the demonstrators hurled rocks, water bottles and bricks in return, said one of the protesters, a 27-year-old man surnamed Chen.

It is the second major protest in two weeks in a corner of coastal southern China that has seen periodic unrest over the past few years, primarily over land disputes. In much of Guangdong province, conflicts have been intense because the area is among China's most economically developed, pushing up land prices.

In Wukan, a village to the southwest of Haimen, protesters drove local authorities from the area nearly two weeks ago over a land dispute. Wukan protesters reached by phone yesterday said plans for a large march on a nearby government office today would go ahead.

In Haimen, some protesters clashed with police, leaving dozens hurt. "We don't have weapons, only mineral water bottles and we threw them at the police but they used batons to beat people up," Chen said.